5.3.7: Negative feedback (HT only)
Not started yet — this one needs some love.
Adrenaline is produced by the adrenal glands in times of fear or stress.
Adrenaline increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles.
Adrenaline prepares the body for flight or fight.
Thyroxine is produced by the thyroid gland and stimulates the basal metabolic rate.
Thyroxine has an important role in growth and development.
Thyroxine levels are controlled by negative feedback.
In negative feedback, a change away from the normal level triggers responses that return the level towards normal.
Simple negative-feedback diagrams should be interpreted by identifying the change, the hormone response and how the response reverses the change.
Common exam mistakes
Do not call adrenaline a nerve impulse; it is a hormone produced by adrenal glands.
Adrenaline prepares for flight or fight by increasing heart rate and delivery of oxygen and glucose, not by directly making muscles contract.
Thyroxine controls basal metabolic rate; do not confuse it with insulin or adrenaline.
Negative feedback reverses a change; do not describe it as making the change bigger.
In feedback diagrams, follow the arrows carefully and state which hormone level rises or falls.